S811
Clinical - Lung
ESTRO 2026
esophagus dose (MED). Robust 3D IMPT (allowing 15 mm maximum target motion) plans were created using two or three beams using the average CT, including 5-layer rescanning. Daily online position verification included body-surface scanning, 2D kV imaging, and cone-beam CT imaging. Weekly repeated 4D-CTs were acquired and delivered dose evaluated; treatment plans were adapted when target coverage was inadequate. Data on side effects were prospectively collected. Results: Seventeen patients met at least one of the predefined Δ NTCP thresholds and were eligible for IMPT. Median CTV was 114 cm3 (range 51-601). Compared to VMAT, IMPT resulted in lower NTCP for ACE in all patients. In 6 patients (38%), IMPT also resulted in ≥ 10% lower NTCP for AET compared to VMAT (Table 1; Figure 1). IMPT treatment plans yielded significantly lower MHD (7.4 Gy vs. 13.3 Gy; p=0.002), MLD (6.0 Gy vs. 11.0 Gy; p<0.001), and MED (3.4 Gy vs. 8.9 Gy; p<0.001) compared to VMAT (Figure 1.).Grade ≥ 2 AET was observed in 2 patients (11.8%). After a median follow- up of 39 months (range 4-62 months), no cases of RP or ACE were reported, and all patients were alive. Follow-up data will be updated continuously and all newly treated patients will be added to the prospective registry.
guided adaptive hypo-RT is a promising treatment strategy in unresectable stage III NSCLC. It significantly reduced G2+ respiratory toxicity while maintaining non-inferior PFS. This approach represents a step toward personalized, toxicity-sparing radiotherapy. References: [1] Wang D, Liu S, Fu J, Zhang P, Zheng S, Qiu B, Liu H, Ye Y, Guo J, Zhou Y, Jiang H, Yin S, He H, Xie C, Liu H. Correlation of Ktrans derived from dynamic contrast- enhanced MRI with treatment response and survival in locally advanced NSCLC patients undergoing induction immunochemotherapy and concurrent chemoradiotherapy. J Immunother Cancer. 2024 Jun 23;12(6):e008574.[2] Zhou R, Liu F, Zhang H, Wang D, Zhang P, Zheng S, Liu Y, Chen L, Guo J, Zou Y, Rong YM, Liu H, Qiu B. Fraction Dose Escalation of Hypofractionated Radiotherapy with Concurrent Chemotherapy and Subsequent Consolidation Immunotherapy in Locally Advanced Non-Small Cell Lung Cancer: A Phase I Study. Clin Cancer Res. 2024 Jul 1;30(13):2719-2728. Keywords: Lung cancer, hypofractionated radiotherapy, MRI Intensity modulated proton radiotherapy for thymoma patients: NTCP model-based selection and first results. Robin Wijsman, Olga Chouvalova, Pieter R.A.J. Deseyne, Agata Bannink-Gawryszuk, Fred F. Ubbels, Stefan Both, Erik W. Korevaar, Stefanie A. De Boer, Johannes A. Langendijk Radiation Oncology, University Medical Center Groningen, Groningen, Netherlands Purpose/Objective: In October 2019, intensity modulated proton radiotherapy (IMPT) was introduced for patients with thymic tumours. Allocation of IMPT was based on model-based selection (MBS). The objective of this prospective study was to evaluate MBS in this patient group and to report initial findings on treatment- Poster Discussion 3207
related side effects. Material/Methods:
Thymoma or thymic carcinoma patients referred for curative-intent radiotherapy were selected for IMPT in accordance with the national indication protocol for MBS (Table 1). MBS was based on differences in NTCP ( Δ NTCP) between VMAT and IMPT plans for the following endpoints: Acute Coronary Events (ACE; threshold ≥ 2%), Grade ≥ 2 radiation pneumonitis (RP; threshold ≥ 10%), and Grade ≥ 2 acute esophageal toxicity (AET; threshold ≥ 10%). The NTCP models included the following dosimetric parameters: mean heart dose (MHD), mean lung dose (MLD), and mean
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